Children as young as 10 were injured in the clashes and one police officer was hospitalised .

Cleveland Police said five people were arrested but more are expected as the investigation into the disorder continues.

The violence started following a pitch invasion by some Sheffield United fans after the visiting side thought they'd snatched a late equaliser against Boro, only for the goal to be disallowed.

The violence started following a pitch invasion by some Sheffield United fans (Image: Action Images)

The violence then continued outside the ground, with hundreds of fans involved and dozens of police and stewards called to try and keep the situation under control, the Gazette Liver reports .

One Sheffield United fan told The Gazette that fans were "chucking things at each other", adding: "It got heated."

Cleveland Police have now issued a statement condemning the violence and launching an investigation.

Rival fans clashed in the stands (Image: Rex Features)

They say a police officer was injured and taken to hospital and that five people have so far been arrested on suspicion of a number of offences.

Those arrested are currently in police custody, though the number is expected to rise as the investigation into the violence unfolds.

Children as young as 10 were injured in the clashes (Image: Rex Features)

Assistant Chief Constable Jason Harwin said: “We will absolutely not tolerate violence of this nature and we will work to identify the offenders and bring them to justice.

“The vast majority of fans accept that football is a family game, watched by children, parents and grandparents. It’s terrifying for children to witness such violence, or be innocently embroiled in it as their parents frantically try to keep them safe.

“Unfortunately a small minority of people behave in a manner which puts innocent fans at risk. We will be working closely with Middlesbrough Football Club and Sheffield United as part of our investigations.”

Anyone with information, or who may have any images that may help police with their investigations are asked to call Cleveland Police on the non-emergency number 101.